🤖 RoboServo

A lightweight servo control library for ESP32, ESP8266, nRF52/nRF53, RP2040, STM32, AVR, UNO R4, UNO Q, and Mbed

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✨ Features

• 🎯 Simple API — Familiar Arduino Servo-style interface
• 📦 Multi-servo support — Up to 8 servos (6 on smaller variants)
• 🔄 Servo types — 180°, 270°, 360° continuous, or custom angles
• ⚡ High precision — 14-bit PWM (ESP32) / 10-bit PWM (ESP8266)
• 🔧 Configurable — Adjustable frequency (40-400Hz) and pulse width
• 🏎️ High-speed PWM — 333Hz digital servos and kHz motor/ESC outputs via RoboMotor
• 🧵 Thread-safe — Safe channel allocation for RTOS (ESP32)

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📋 Supported Boards

Chip	Max Servos	PWM Resolution	Status
ESP32	8	14-bit	✅
ESP32-S2	8	14-bit	✅
ESP32-S3	8	14-bit	✅
ESP32-C3	6	14-bit	✅
ESP32-C6	6	14-bit	✅
ESP32-H2	6	14-bit	✅
ESP32-P4	8	14-bit	✅
ESP8266	8	10-bit	✅
ArduinoNRF nRF52	8	10-bit	✅
Adafruit / nRF52 DK	6	10-bit	✅
RP2040 / RP2350	8	10-bit	✅
STM32	6	10-bit	✅
AVR (UNO/Nano)	6	8-bit (ISR)	✅
AVR (Mega)	12	8-bit (ISR)	✅
UNO R4 Minima / WiFi	8	10-bit	✅
UNO Q	6	10-bit	✅
Mbed (Nano 33 BLE)	8	10-bit	✅
nRF5340 (generic core)	6	10-bit	✅

High-Speed PWM Outputs (RoboMotor)

Chip	Max Motors	Default Freq	PWM Resolution	Mix with 50Hz Servo
ESP32	4	20 kHz	10-bit	✅ (isolated timer group)
ESP32-S2 / S3	4	20 kHz	10-bit	✅
ESP32-C3 / C6 / H2	2	20 kHz	10-bit	✅
ESP32-P4	4	20 kHz	10-bit	✅
ESP8266	4	20 kHz	10-bit	❌ (global single frequency)
ArduinoNRF nRF52	4	20 kHz	10-bit	✅ (per-pin frequency groups)
Adafruit / nRF52 DK	2	20 kHz	10-bit	❌ (shared frequency)
RP2040 / RP2350	2	20 kHz	10-bit	❌ (shared frequency)
STM32	2	20 kHz	10-bit	❌ (shared frequency)
AVR	—	—	—	❌ (servo only)
UNO R4 / UNO Q / Mbed	—	—	—	❌ (servo only)

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🚀 Quick Start

Installation

Arduino IDE 2.x (Library Manager):
Select an ESP32, ESP8266, nRF52, RP2040, STM32, or AVR board, then Tools → Manage Libraries… → search RoboServo → Install.

Arduino IDE (ZIP):
Sketch → Include Library → Add .ZIP Library...

PlatformIO:

lib_deps = https://github.com/dunknowcoding/RoboServo.git#v1.1.2

Basic Example

#include <RoboServo.h>

RoboServo myServo;

void setup() {
    myServo.attach(13);   // Attach to GPIO 13
    myServo.write(90);    // Move to 90°
}

void loop() {
    myServo.write(0);
    delay(1000);
    myServo.write(180);
    delay(1000);
}

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📖 API Reference

RoboServo Class

Attachment

uint8_t attach(int pin);
uint8_t attach(int pin, int minPulseUs, int maxPulseUs);
uint8_t attach(int pin, int minPulseUs, int maxPulseUs, RoboServoType type);
uint8_t attach(int pin, int minPulseUs, int maxPulseUs, int maxAngle);
uint8_t attach(int pin, int minPulseUs, int maxPulseUs, RoboServoType type, int frequency);

void detach();
bool attached();

Position Control

void write(int angle);               // Set angle (0 to maxAngle)
void writeMicroseconds(int pulseUs); // Set pulse width directly
int read();                          // Get current angle
int readMicroseconds();              // Get current pulse width

Configuration

void setServoType(RoboServoType type);   // SERVO_TYPE_180, _270, _360, _CUSTOM
void setMaxAngle(int angle);              // Custom max angle
void setPulseLimits(int minUs, int maxUs);
void setFrequency(int frequency);         // 40-400 Hz (default: 50)

RoboServoType getServoType();
int getMaxAngle();
int getMinPulse();
int getMaxPulse();
int getFrequency();
int getPin();

360° Continuous Servo

void setSpeed(int speed);  // -100 (full reverse) to +100 (full forward)
void stop();               // Stop rotation (center pulse)
void release();            // Release PWM signal (go limp)

Static Methods

static int getAttachedCount();
static uint32_t getDefaultFrequency();  // 50 Hz
static uint8_t getServoResolution();    // 14-bit

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RoboServoGroup Class

Control multiple servos as a coordinated group.

// Add/Remove
int addServo(int pin);
int addServo(int pin, int minPulseUs, int maxPulseUs, RoboServoType type);
bool removeServo(int index);
void removeAll();

// Info
int count();
RoboServo* getServo(int index);

// Group Control
void writeAll(int angle);
void writeAllMicroseconds(int pulseUs);
void writeMultiple(const int* angles, int count);
void stopAll();
void detachAll();

// Individual Control
void write(int index, int angle);
void writeMicroseconds(int index, int pulseUs);
int read(int index);

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High Refresh-Rate Servos (333–400 Hz)

Standard RoboServo API — attach at a higher frequency for digital servos that support it:

#include <RoboServoHighSpeed.h>

RoboServo servo;
roboServoAttachHighSpeed(servo, 13);   // 333 Hz, 500-2500 us
servo.write(90);

Or set frequency manually: servo.attach(13, 500, 2500, SERVO_TYPE_180, 333);

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RoboMotor Class

High-frequency PWM for motor driver enable pins and ESC inputs (1–40 kHz, default 20 kHz).

Attachment

uint8_t attach(int pin);
uint8_t attach(int pin, int frequency);
uint8_t attach(int pin, int frequency, uint8_t resolution);

void detach();
bool attached();

Duty Cycle Control

void write(int dutyPercent);    // 0-100 %
void writeRaw(uint32_t duty);   // 0 to 2^resolution - 1
int read();                     // Current duty %
uint32_t readRaw();             // Current raw duty

Configuration

void setFrequency(int frequency);   // 1000-40000 Hz (default: 20000)
int getFrequency();
uint8_t getResolution();
int getPin();
uint8_t getChannel();

Motor Control

void stop();    // 0% duty
void brake();   // Alias for stop()

Static Methods

static int getAttachedCount();
static uint32_t getDefaultFrequency();  // 20000 Hz
static uint8_t getMotorResolution();    // 10-bit

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RoboMotorGroup Class

Control multiple motors as a coordinated group.

// Add/Remove
int addMotor(int pin);
int addMotor(int pin, int frequency);
bool removeMotor(int index);
void removeAll();

// Info
int count();
RoboMotor* getMotor(int index);

// Group Control
void writeAll(int dutyPercent);
void writeMultiple(const int* duties, int count);
void stopAll();
void detachAll();

// Individual Control
void write(int index, int dutyPercent);
int read(int index);

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🎛️ Servo Types

// Standard 180° servo (default)
servo.attach(13, 500, 2500, SERVO_TYPE_180);
servo.write(90);  // Center position

// Extended 270° servo  
servo.attach(13, 500, 2500, SERVO_TYPE_270);
servo.write(135); // Center position

// Custom angle range (e.g., 120°)
servo.attach(13, 500, 2500, 120);
servo.write(60);  // Center position

// Continuous rotation 360° servo
servo.attach(13, 500, 2500, SERVO_TYPE_360);
servo.setSpeed(50);   // 50% forward
servo.setSpeed(-50);  // 50% reverse
servo.stop();         // Stop rotation

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🔌 Valid GPIO Pins

Variant	Valid Pins
ESP32	2, 4, 5, 12-19, 21-23, 25-27, 32-33
ESP32-S2	1-21, 26, 33-42
ESP32-S3	1-21, 35-45, 47-48
ESP32-C3	0-10, 18-21
ESP32-C6	0-23
ESP32-H2	0-14, 25-27
ESP32-P4	0-54 (except 24-25)
ESP8266	0-5, 12-16
ArduinoNRF nRF52	PWM-capable pins (see board variant)
Adafruit / nRF52 DK	PWM-capable pins (see core docs)
RP2040 / RP2350	PWM-capable pins (digitalPinHasPWM)
STM32	PWM-capable pins (digitalPinHasPWM)
AVR (UNO/Nano/Mega)	Any digital pin (Timer1 ISR)
UNO R4	PWM-capable pins (digitalPinHasPWM)
UNO Q	Digital pins with counter_servo support
Mbed (Nano 33 BLE)	Any digital pin (20 ms Ticker frame)
nRF5340 DK	PWM-capable pins (core-dependent)

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🔧 Wiring

ESP32                    Servo
─────                    ─────
GPIO x  ──────────────►  Signal (Orange/White)
5V      ──────────────►  VCC (Red)
GND     ──────────────►  GND (Brown/Black)

⚠️ Power Tip: Use an external 5V power supply (~1A per servo) when driving multiple servos. The ESP32's 5V pin cannot supply enough current.

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⚡ Timer Conflicts

RoboServo uses PWM at 50Hz by default. Conflicts may occur if analogWrite() uses different settings.

ESP32 Solutions:

Method	Description
Order matters	Call analogWrite() before servo.attach()
Use LEDC directly	Replace analogWrite() with ledcAttach() + ledcWrite()
Match frequency	analogWriteFrequency(pin, 50)

ESP8266 Notes:

• All PWM channels share the same frequency
• RoboServo sets the global PWM frequency on attach()
• For best results, use the same frequency for all PWM outputs
• RoboMotor cannot run alongside RoboServo — pick one domain per sketch

nRF52 / RP2040 / STM32 Notes:

• ArduinoNRF boards use per-pin frequency groups via nrfPwmSetPinFrequency
• Adafruit nRF52, RP2040, and STM32 cores share a single PWM frequency per sketch
• RoboServo sets frequency on attach(); avoid mixing different frequencies
• RoboMotor on shared-frequency cores is limited to 2 outputs and cannot mix 50Hz servo with 20kHz motor

AVR Notes:

• Uses Timer1 compare interrupts (same resource as Tone and the built-in Servo library)
• Do not mix with Tone() or the Arduino Servo library in the same sketch
• RoboMotor is not supported on AVR — use RoboServo for 50Hz hobby servos only

UNO R4 / UNO Q / Mbed Notes:

• UNO R4 uses FSP PWM with a 20 ms frame configured in microseconds
• UNO Q requires the board counter_servo device (provided on the UNO Q variant)
• Mbed boards use a 20 ms Ticker + GPIO pulse backend (not analogWrite at 500 Hz)
• UNO Q: install Arduino_RouterBridge from Library Manager (required by the Zephyr core)
• RoboMotor is not supported on UNO R4, UNO Q, Mbed, or AVR

nRF5340 Notes:

• Detected via ARDUINO_ARCH_NRF53 / NRF5340_XXAA macros
• Mbed and Zephyr nRF5340 cores use the Mbed/Zephyr backends above
• Other nRF5340 Arduino cores fall back to shared-frequency analogWrite

RoboMotor on ESP32:

• Motor outputs use a separate LEDC channel group (above channel 7) to avoid interfering with 50Hz servos
• See ServoAndMotor for mixed low-speed servo + high-speed motor usage

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📁 Examples

Example	Description
BasicServo	Single servo sweep
PlatformSmoke	Minimal attach/write (no Serial, for UNO Q / CI)
MultipleServos	Independent multi-servo control
ServoGroup	Coordinated group movements
Servo360	Continuous rotation control
ServoTypes	180°, 270°, custom angles
CustomPulseWidth	Pulse calibration tool
ServoWithPWM	Coexisting with LED PWM
ADCServoControl	Potentiometer control
HighSpeedServo	333Hz digital servo sweep
MotorPwm	20kHz motor duty cycle ramp
MotorGroup	Coordinated multi-motor control
ServoAndMotor	50Hz servo + 20kHz motor together

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🔍 Troubleshooting

Problem	Solution
Servo not moving	Check 5V power supply; verify GPIO is valid for your board
Servo jittering	Use external power; add 100μF capacitor near servo
Limited rotation range	Calibrate pulse width (try 1000-2000μs range)
Stops after analogWrite()	Timer conflict — see solutions above
attach() returns 255	No channels available, invalid pin, or pin already in use
Motor not spinning	Verify driver wiring; RoboMotor drives PWM enable, not direction pins

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📄 License

MIT License — see LICENSE for details.

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Made with ❤️ for the embedded robotics community

_{v0.5.0 • Supports ESP32, ESP8266, nRF52/nRF53, RP2040, STM32, AVR, UNO R4, UNO Q, Mbed}